A steering column system constitutes a critical safety securing component of a vehicle, and it is very important how to control the behavior thereof at the time of a crash in order to secure the safety of an occupant when he or she is involved in the crash. Normally, an impact energy absorbing mechanism is provided in a steering column system itself, and the steering column system plays an important role as a supporting member of an air bag that is encased within a steering wheel.
On the other hand, in order for drivers to have their optimum driving postures, general steering column systems are constructed such that the tilt angle of the steering wheel can be adjusted and the axial position of the steering wheel can be adjusted according to the builds and driving postures of the drivers. Consequently, the steering column systems are required to have contradicting functions to facilitate the adjustment of the position and posture of the column main body (that is, the steering wheel) and to secure predetermined position and posture at the time of a crash. In conventional steering column systems, various devices have been made to make these contradicting functions compatible, however, in association with the users' demands for operability increasing, further improvements are required.
Here, in Patent Document No. 1, a steering column system is disclosed in which a column main body can be held by superimposing a multiplicity of friction plates one on another and making use of frictional force generated therebetween.    Patent Document No. 1: Japanese Patent Unexamined Publication JP-A-10-35511    Patent Document No. 2; Japanese Patent Unexamined Publication JP-A-9-221043    Patent Document No. 3: European Patent Examined Publication EP-1394012-B1    Patent Document No. 4: European Patent Examined Publication EP-796780-B1    Patent Document No. 5: U.S. patent Examined Publication U.S. Pat. No. 6,390,717